1. Field of the Invention
The present invention relates to a novel compound obtained from a natural plant and more particularly to a compound which is extracted from a woody climbing plant belonging to the Celastaceae family and inhibits the activity of xcex1-glucosidase, and further to an antidiabetic and dieting agent containing the compound and a method for producing such a compound.
2. Prior Art
In recent years, among therapeutic drugs classified as antidiabetic agents, xcex1-glucosidase inhibitors which inhibit the activity of xcex1-glucosidase have been widely used in the treatment of diabetes and prediabetes. xcex1-glucosidase is an enzyme that breaks down disaccharides or Strisaccharides and glucides such as starch, etc., that are present on the mucous membranes of the digestive tract.
As universally known, natural medicines and medicinal foodstuffs, which can be safely and easily supplied in the diet and can inhibit the onset of hyperglycemia, are constantly in demand.
Accordingly, natural drugs used in various traditional systems of medicine around the world have attracted attention as a means of developing natural medicines that do not originate in chemically synthesized products.
In research and development for developing such natural medicines, the inventor of the present invention has made special efforts in the development of antidiabetic agents.
In this research, the inventor has focused special attention on Salacia reticulate. Salacia reticulata belongs to the Celastaceae family, known in Singhalese as Kotala himbutuwel, which has been used since ancient times in the traditional medicine of India and Sri Lanka, i.e. in the Ayurvedic medical tradition. In rat experiments by the inventor, an aqueous extract (watersoluble fraction) of this substance has shown a superior effect in inhibiting hyperglycemia following sucrose or maltose loading (i.e., this substance has strongly inhibited the increase of blood sugar levels after the administration of sucrose or maltose in rats). In other words, the inventor has ascertained that the above-described extract is effective in inhibiting the activity of xcex1-glucosidase, an enzyme that as described above breaks down disaccharides, etc.
Furthermore, the inventor has also ascertained that an aqueous extract of Salacia reticulata belonging to the Celastaceae family inhibits the activity of xcex1-glucosidase, i.e., maltase and sucrase, present in the intestines of rats (the fraction inhibited rat intestinal maltase and sucrase).
Furthermore, the present inventor is investigating the active principle that manifests the hyperglycemia-inhibiting effect in Salacia reticulata of the Celastaceae family.
The inventor has also screened plants other than Salacia reticulata, which is a plant belonging to the above-described Celastaceae family, in a search for plants that inhibit the activity of xcex1-glucosidase.
As a result, the inventor discovered that there is an extremely strong xcex1-glucosidase inhibiting effect in aqueous extracts of Salacia prinoides and Salacia oblonga belonging to the Celastaceae family, and especially in an aqueous extract of the former plant.
More specifically, the inventor, by extracting and fractionating Salacia prinoides, succeeded in discovering a novel compound which has an inhibitory effect against isomaltose (a type of disaccharide) that is more than 200 times stronger than that of the xcex1-glucosidase inhibiting agent Acarbose (manufactured by Bayer Corp., Trademark Glucobay), which is a commercially marketed drug. The Acarbose is a type of sugar that is, like antibiotics, produced by the genus Actinoplanes (a certain type of Actinomyces).
The present invention was created based upon these findings.
Accordingly, the object of the present invention is to provide a novel compound which is extracted from the woody climbing plants Salacia prinoides and Salacia oblonga and is superior in terms of its characteristic of inhibiting the activity of xcex1-glucosidase (hereafter this compound may be referred to as an xe2x80x9cxcex1-glucosidase inhibitorxe2x80x9d).
Another object of the present invention is to provide an antidiabetic agent or dieting agent which utilizes the above-described compound having the effect in inhibiting xcex1-glucosidase (which is an enzyme that breaks down disaccharides, etc. that are present on the mucous membranes of the digestive tract).
Still another object of the present invention is to provide a method for producing or extracting the above-described compound that has the superior characteristics of inhibiting xcex1-glucosidase activity.
In the present invention, the above-described novel compound (xcex1-glucosidase inhibitor) that has the superior characteristic of inhibiting xcex1-glucosidase activity is obtained by extraction and fractionation from plants belonging to the natural plant Celastaceae family, i.e., Salacia prinoides and/or Salacia oblonga, which have been utilized as natural drugs. Accordingly, the present invention provides an antidiabetic agent and dieting agent that are superior in terms of safety compared to chemically synthesized products.
More specifically, the present invention provides the compound itself that is expressed by the Chemical Structural Formula shown below, which was discovered in the woody climbing plants Salacia prinoides or Salacia oblonga. In the following description, the compound expressed by the Chemical Structural Formula shown below may be referred to as the xe2x80x9cnovel compound SP (SP merely called after Salacia Prinoides)xe2x80x9d.
Chemical Structural Formula 
Furthermore, the present invention provides an antidiabetic agent which utilizes the property of effectively inhibiting the activity of xcex1-glucosidase (an enzyme that breaks down disaccharides, etc.) shown by the compound expressed by the above Chemical Structural Formula The present invention further provides a dieting agent used to prevent obesity caused by excessive nutrition, which utilizes the xcex1-glucosidase inhibiting effect of the compound shown by the above Chemical Structural Formula in order to prevent the breakdown of various types of glucides and oligosaccharides (disaccharides or trisaccharides) ingested in meals into monosaccharides and the absorption of such monosaccharides in the body. These applied products were not known at the time of the previous research and development work concerning Salacia reticulata. 
Moreover, the present invention provides a method for extracting the novel compound expressed by the above Chemical Structural Formula which is superior in terms of its characteristic of inhibiting the activity of xcex1-glucosidase. In this method, Salacia prinoides and/or Salacia oblonga of the Celastaceae family are subjected to an extraction process using heated methanol, the methanol extract thus obtained are subjected to a partition treatment using ethyl acetate and water, and the portion migrating into the water is then subjected to a fractionation treatment by means of chromatography.